Add solution #440

Author: JoshCrozier

README.md

@@ -349,6 +349,7 @@
 436|[Find Right Interval](./0436-find-right-interval.js)|Medium|
 437|[Path Sum III](./0437-path-sum-iii.js)|Medium|
 438|[Find All Anagrams in a String](./0438-find-all-anagrams-in-a-string.js)|Medium|
+440|[K-th Smallest in Lexicographical Order](./0440-k-th-smallest-in-lexicographical-order.js)|Hard|
 441|[Arranging Coins](./0441-arranging-coins.js)|Easy|
 442|[Find All Duplicates in an Array](./0442-find-all-duplicates-in-an-array.js)|Medium|
 443|[String Compression](./0443-string-compression.js)|Medium|

solutions/0440-k-th-smallest-in-lexicographical-order.js

@@ -0,0 +1,35 @@
+/**
+ * 440. K-th Smallest in Lexicographical Order
+ * https://leetcode.com/problems/k-th-smallest-in-lexicographical-order/
+ * Difficulty: Hard
+ *
+ * Given two integers n and k, return the kth lexicographically smallest integer in
+ * the range [1, n].
+ */
+
+/**
+ * @param {number} n
+ * @param {number} k
+ * @return {number}
+ */
+var findKthNumber = function(n, k) {
+  let result = 1;
+  k--;
+
+  while (k > 0) {
+    let count = 0;
+    for (let first = result, last = result + 1; first <= n; first *= 10, last *= 10) {
+      count += Math.min(n + 1, last) - first;
+    }
+
+    if (count <= k) {
+      result++;
+      k -= count;
+    } else {
+      result *= 10;
+      k--;
+    }
+  }
+
+  return result;
+};